This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-353171, filed Dec. 13, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a method of manufacturing a disc drive such as a DVD drive, to an apparatus for manufacturing the optical disc drive, and to the optical disc drive.
FIG. 5 shows a conventional optical disc drive such as a DVD drive. A disc table 2 is fitted on a rotational shaft 1a of a spindle motor 1 serving as a drive motor. An optical disc 3 such as a DVD disc is supported on the disc table 2 and rotated.
An important requirement for the optical disc drive is the xe2x80x9csurface precisionxe2x80x9d of a disc mounting surface 2a of the disc table 2 relative to an axis S of the spindle motor rotational shaft 1a (i.e. the precision of the level of the disc mounting surface relative to the rotational shaft while the surface is being rotated). If there occurs even a slight surface run-out of the disc table 2 (i.e. xe2x80x9cwobblingxe2x80x9d of the table 2) while the rotational shaft 1a is being rotated, the surface of the optical disc 3 will similarly wobble, resulting in defective information reproduction or recording.
In particular, in a DVD drive which requires high rotational precision, a brushless motor is used as the spindle motor 1. In order to enhance the surface precision of the disc table 2, the run-out of the disc mounting surface 2a of the disc table 2 is detected after the DVD drive is assembled as shown in FIG. 5. Then, the disc table 2 is removed from the rotational shaft 1a of the spindle motor 1, and the disc mounting surface 2a of the disc table 2 is machined to reduce the run-out.
Specifically, half-blanking is carried out to form three projecting portions from the back side of the disc mounting surface 2a of disc table 2. The three projections are disposed equidistantly in a circle defined at the same radial distance on the back surface of the disc mounting surface 2a. A plane defined by the three points of these projecting portions is adjusted so as to become perpendicular to the axis S of the rotational shaft 1a. 
FIG. 6 shows a CD drive which requires less mechanical rotational precision than the DVD drive. Thus, a general-purpose brushed motor (a motor with a brush), etc. can be used as a spindle motor 1A and the manufacturing cost can be reduced accordingly.
That surface of the spindle motor 1A, from which a rotational shaft 1a projects, is placed on a chassis 4 and fixed by attachment screws 5. A disc table 2a is fitted on the rotational shaft 1a by means of press-fitting, etc.
In this CD drive, as shown in FIG. 7, in order to eliminate the surface run-out, a cutting process is performed to make a disc mounting surface 2a of disc table 2A perpendicular to the axis S of the rotational shaft 1a in the state in which the disc table 2A is fitted on the rotational shaft 1a that has been removed from the spindle motor 1A. Thereafter, the rotational shaft 1a with the disc table 2A is assembled into the spindle motor 1A.
In the case of the DVD drive shown in FIG. 5, however, the manufacturing cost increases because the run-out of the disc mounting surface 2a is measured once the DVD drive has been assembled, following which the DVD drive is disassembled, the disc table 2 is machined and the drive is assembled once again. Furthermore, since the expensive brushless motor is used as spindle motor 1, the manufacturing cost increases.
On the other hand, in the case of the CD drive shown in FIG. 6, when a commercially available optical disc with low precision of the center of gravity is mounted and rotated, even if a high-prevision brushed motor is used, the rotational shaft 1a is rotated with an elastic deformation caused by centrifugal force due to mass eccentricity of the optical disc. As a result, the precision in rotation deteriorates and satisfactory reproduction/recording cannot be performed.
A first object of the present invention is to provide a disc drive, such as a DVD drive requiring high rotational precision, which is realized with a simple, inexpensive structure like a CD drive.
According to an aspect of the invention, there is provided an apparatus for manufacturing a disc drive, the apparatus comprising: urging means, put in contact with a disc table engaged with a rotational shaft of a drive motor via an engaging portion, for varying an inclination of the disc table which is swingable with a point of support at the engaging portion; detection means for detecting, in a non-contact state, the inclination of the disc table varied by the urging means; control means for receiving a detection signal from the detection means and stopping rotation of the drive motor when the inclination of the disc table has decreased to a predetermined value or less; and fixing means for fixing the disc table to the rotational shaft of the drive motor which has been stopped by the control means.
According to the present invention, even in a case of a disc drive requiring high rotational precision, a disc table can be fixed to a rotational shaft of a spindle motor while the position of the disc table is being adjusted. Therefore, a mechanism with a simple, inexpensive structure can be obtained.
A second object of the invention is to provide an optical disc drive wherein, even when an optical disc such as a disc with mass eccentricity, which may deteriorate precision in rotation, is to be driven, run-out of the disc table can be exactly limited and high rotational precision is maintained, and therefore the reliability in information reproduction/recording can be enhanced.
According to another aspect of the invention, there is provided an optical disc drive comprising: a drive motor; a disc table for mounting of an optical disc, the disc table being fixed to a rotational shaft of the drive motor; reproducing/recording means for effecting information reproduction/recording by radiating a laser beam to the optical disc; a chassis fixed to a rotational shaft projection surface of the drive motor; and a bearing member, provided on the chassis, for supporting the rotational shaft of the drive motor, which is located near the disc table.
According to the invention, the rotational shaft is supported at two points within the motor body and it is also supported at a third point by the bearing member. Therefore, the occurrence of centrifugal force due to mass eccentricity of the disc can be prevented.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.